PHP notice error when template part is created

[wildworks]

Originally reported in the Gutenberg repository: ​https://github.com/WordPress/gutenberg/issues/48596

I get a PHP notice error when adding a new template part in the site editor.

PHP Notice:  Trying to get property 'area' of non-object in /var/www/src/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php on line 581

When adding a new template part, the $template variable will be null, so this error would occur.

Original Report:

Reporter: @chrystl

Description

I get the notice below with WordPress 6.2-beta3-55428 and and Twenty Twenty Three (only) when creating a new TP from the TP block inside a TP.

[PHP Notice:  Trying to get property 'area' of non-object in /wp-single/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php on line 586
[PHP Stack trace:
[PHP   1. {main}() /wp-single/index.php:0
[PHP   2. require() /wp-single/index.php:17
[PHP   3. wp() /wp-single/wp-blog-header.php:16
[PHP   4. WP->main() /wp-single/wp-includes/functions.php:1330
[PHP   5. WP->parse_request() /wp-single/wp-includes/class-wp.php:780
[PHP   6. do_action_ref_array() /wp-single/wp-includes/class-wp.php:399
[PHP   7. WP_Hook->do_action() /wp-single/wp-includes/plugin.php:565
[PHP   8. WP_Hook->apply_filters() /wp-single/wp-includes/class-wp-hook.php:332
[PHP   9. rest_api_loaded() /wp-single/wp-includes/class-wp-hook.php:308
[PHP  10. WP_REST_Server->serve_request() /wp-single/wp-includes/rest-api.php:410
[PHP  11. WP_REST_Server->dispatch() /wp-single/wp-includes/rest-api/class-wp-rest-server.php:442
[PHP  12. WP_REST_Server->respond_to_request() /wp-single/wp-includes/rest-api/class-wp-rest-server.php:1028
[PHP  13. WP_REST_Templates_Controller->create_item() /wp-single/wp-includes/rest-api/class-wp-rest-server.php:1181
[PHP  14. WP_REST_Templates_Controller->prepare_item_for_database() /wp-single/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php:400

Step-by-step reproduction instructions

1. go to /wp-admin/site-editor.php?canvas=view&path=%2Fwp_template_part&postType=wp_template_part then edit the Footer TP for example
2. add a TP block > choose "start blank" > then create your TP. This action triggers the PHP notice mentioned above.

Environment

• WordPress: 6.1.1, 6.2-beta3-55428
• PHP: 7.2.3

Trac ticket: https://core.trac.wordpress.org/ticket/57851

Originally reported in the Gutenberg repository: ​https://github.com/WordPress/gutenberg/issues/48596

This PR fixes the PHP notice error when template part is created.

PHP Notice:  Trying to get property 'area' of non-object in /var/www/src/wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php on line 581

When adding a new template part, the $template variable will be null, so this error would occur. I think we need to consider both cases, when the $template part is null or when the area property is empty.

[hellofromTonya]

Hello @wildworks and @chrystl.

Welcome back to WordPress Core's Trac. Thanks for bringing the report here.

I've coped notes from the original report and added them to the ticket's description.

[dunhakdis]

Was able to reproduce this issue as well. Thanks for submitting a PR, added a comment to use empty().

[audrasjb]

Self assigning for review